​Per Delsing and PhD Ida-Maria Svensson in the lab. In the white cylinder, the cryostat, there are extremely cooled quantum bits whose lifetime the researchers are measuring. Photo: Johan Bodell​​

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Now the quantum computer will become reality

​A billion-dollar research effort is to make Sweden a world leader in quantum technology. Now, Chalmers researchers have begun work on developing a quantum computer with far greater computational power than today's best supercomputers.​

The days are currently full of interviews. Per Delsing, Professor of quantum device physics at Chalmers, is busy recruiting high-level researchers and doctoral students to help pull through a very challenging project: building a quantum computer that far exceeds today's best computers.

"To get the right staff is the alpha and omega of it all. But it looks promising, we have received many good applications", says Per Delsing.

The development of the quantum computer is the main project in the ten-year research program Wallenberg Centre for Quantum Technology, launched at the turn of the year, thanks to a donation of SEK 600 million from the Knut and Alice Wallenberg Foundation. With additional funds from Chalmers, industry and other universities, the total budget is landing nearly SEK 1 billion.

The goal is to make Sweden a leading player in quantum technology. Indeed, recent research in quantum technology has placed the world on the verge of a new technology revolution – the second quantum revolution.

​The first quantum revolution took place in the 20th century, when one learned to utilize quantum mechanical properties of light and material. This led, among other things, to the laser and transistor – inventions that underpin information technology that largely shape today's society.

Now scientists have also learned to control individual quantum systems as individual atoms, electrons and photons, which opens up new opportunities. In sight, there are extremely fast quantum computers, interception-proof communication and hyper-sensitive measurement methods.

Interest is big worldwide. Decision makers and business leaders begin to realize that quantum technology has the potential to greatly change our society, for instance through improved artificial intelligence, secure encryption and more effective design of drugs and materials. Several countries are investing heavily and the EU is launching a scientific flagship in the area next year.

"If Sweden is to continue to be a top level nation, we must be at the forefront here", says Peter Wallenberg Jr.

Several universities and major computer companies, like Google and IBM, are aiming to build a quantum computer. The smallest building block of the quantum computer – the quantum bit or qubit – is based on completely different principles than today's computers (see graphic). This means that you can handle huge amounts of information with relatively few qubits. To surpass the computational power of today's supercomputers, it's enough with 50-60 qubits. The Chalmers researchers aim at reaching at least one hundred qubits within ten years.

"Such a quantum computer could, for example, be used to solve optimization problems, advanced machine learning and heavy calculations of molecule properties," says Per Delsing, who heads the research program.

The Chalmers researchers have chosen to base their quantum computer on superconducting circuits. They have worked with single superconducting qubits for almost 20 years and delivered many contributions to knowledge building within the field. Now they are going to scale up and get many qubits to work together.

At the lab, they are currently working to improve the lifetime of single qubits. Quantum states are extremely sensitive, and collapse if they are exposed to disturbances. Among other things, the researchers paint the inside of the experimental chamber black, so that disturbing microwaves that succeed in slipping through cables will be quickly absorbed. They are also investigating and evaluating different strategies for coupling qubits to each other, which is necessary to be able to perform proper calculations.

"In addition to the lifetime and the coupling of qubits, the number of qubits is an important piece of puzzle to solve. Making many of them is easy, but we need to find smart ways to utilize the equipment to control each of them. Otherwise, it will become very expensive," explains Delsing.

In order for the project to get initiated advice, they are in the process of setting up a scientific advisory board. Per Delsing is currently waiting for answers from eight quantum experts who were asked to be board members.

"They will be a sounding board that we can discuss complex issues with, for instance how fast we should scale up the number of qubits. The technology we need to build the quantum computer is constantly evolving, and it's difficult to determine when it's time to buy it," he says.

On the theory side, the recruitment of competent staff is at the focus right now. Theoretical physicist Giulia Ferrini, expert on quantum computing in continuous variables, was in place already in January and the recruitment process is ongoing with a number of applicants. A total of 15 people will be employed at Chalmers.

"We have received great response and good applicants. Getting the right people is the most important thing – the project does not get any better than the people," says Göran Johansson, Professor of applied quantum physics and one of the main researchers in the quantum computer project.

The theoretical efforts will initially focus on developing a computer model of the quantum computer experiment so that they can help experimentalists forward through simulations.

"A challenge is to identify properties which are important in the model at an early stage, so we don't include too many details when scaling up. Otherwise, we'll hit the ceiling for what a supercomputer can simulate before we reach 40 qubits," says Göran Johansson.

Another important task for the theorists is to explore what a smaller quantum computer can do. With eight thousand well-functioning qubits, one could run the so-called Shor's algorithm – which aroused the world's interest in building quantum computers – and crack today's encryption system. But the first quantum computers, which can do anything beyond what a regular computer can, will be significantly smaller.

"The question is what becomes the breakthrough application for a small quantum computer. We need to find out what kind of problems – that someone is interested in knowing the answer to – a hundred qubit quantum computer can solve," says Göran Johansson.

Here, industrial collaboration comes into the picture – from companies, researchers can get tips for real-life and urgent applications to investigate. The Chalmers researchers have conducted discussions with Astrazeneca, who would have a lot to gain if they could calculate the characteristics of large molecules in their drug development, and Jeppesen who works to optimize aircraft crews and routes. The interest in becoming part of the quantum technology initiative is generally large among companies that have challenges that would be appropriate to solve with a quantum computer.

"They are keen to not miss the train. This can go quite quickly when it's getting started, and then it's important to have skills and be able to speed up at the right pace," says Per Delsing.

Facts about the Wallenberg Center for Quantum Technology

• Wallenberg Center for Quantum Technology is a ten-year initiative aimed at bringing Swedish research and industry to the front of the second quantum revolution.

• The research program will develop and secure Swedish competence in all areas of quantum technology.

• The research program includes a focus project aimed at developing a quantum computer, as well as an excellence program covering the four sub-areas.

• The Wallenberg Center for Quantum Technology is led by and largely located at Chalmers. The areas of quantum communication and quantum sensors are coordinated by KTH and Lund University.

• The program includes a research school, a postdoctoral program, a guest research program and funds for recruiting young researchers. It will ensure long-term Swedish competence supply in quantum technology, even after the end of the program.

• Collaboration with several industry partners ensures that applications are relevant to Swedish industry.